( The whole thing about ReactiveCocoa Our project can be in https://github.com/qianhongqiang/QHQReactive download )

ReactiveCocoa I will not talk about the introduction of , Baidu .ReactiveCocoa This framework is very popular at present , But it's not popular . In the final analysis , The cost of learning is too high , Head file , You hardly know how to use it .ReactiveCocoa Internal implementations use a lot of block, stay block In the case of deep nesting , It's also hard to read the source code . I'm going to do a pull out for you , Break down the modules . Because when I started reading , I don't even know how to start . Source code analysis if there are errors , Welcome to correct .

First of all, let me show you a paragraph ReactiveCocoa Code for

```

   RACSignal *signal = [RACSignal createSignal:^(id subscriber) {
     [subscriber sendNext:[NSDate date]];
     [subscriber sendCompleted];
     return  nil;
   }];
   [signal subscribeNext:^(id x) {
     NSLog(@ "next:%@" , x);
   } error:^(NSError *error) {
     NSLog(@ "error:%@" , error);
   } completed:^{
     NSLog(@ "completed" );
   }];
```
The purpose of this code is to create a model , And subscribe to this model . The code is elegant, isn't it ？ Behind elegance , It always takes a lot of work to support .
Now I'm going to rewrite RAC, It's just a simple version of , The simple version is to keep the main logic , I've dealt with the details . This section only implements the above functions .
Two classes are implemented here QHQSignal and QHQSubscriber
```

@interface QHQSignal ()

@property (nonatomic, copy) void (^didSubscriber)(id subscriber);

@property (nonatomic, strong) QHQSubscriber *scriber;

@end

@implementation QHQSignal

+(QHQSignal *)createSignal:(void (^)(id subscriber))didSubscriber {

QHQSignal *signal = [[self alloc] init];

signal.didSubscriber = didSubscriber;

return signal;

}

-(void)subscribeNext:(void (^)(id))nextBlock {

QHQSubscriber *scriber = [QHQSubscriber subscriberWithNextBlock:nextBlock];

self.scriber = scriber;

self.didSubscriber(self.scriber);

}

@end

```
```

@interface QHQSubscriber ()

@property (nonatomic, copy) void(^nextBlock)(id x);

@property (nonatomic, copy) void(^completionBlock)(id x);

@property (nonatomic, copy) void(^errorBlock)(id x);

@end

@implementation QHQSubscriber

+(instancetype)subscriberWithNextBlock:(void (^)(id x))nextBlock {

return [self subscriberWithNextBlock:nextBlock completionBlock:nil errorBlock:nil];

}

+(instancetype)subscriberWithNextBlock:(void (^)(id x))nextBlock completionBlock:(void (^)(id x))completionBlock errorBlock:(void (^)(id x))errorBlock {

QHQSubscriber *subscriber = [[QHQSubscriber alloc] init];

subscriber.nextBlock = nextBlock;

subscriber.completionBlock = completionBlock;

subscriber.errorBlock = errorBlock;

return subscriber;

}

-(void)sendNext:(id)next {

if (self.nextBlock) {

self.nextBlock(next);

}

}

@end

```
 
QHQSignal Implements a creation method , It needs to be executed when it is created block Pass in ,block There is one subcriber Parameters , That's the internal subscriber of the signal （ in order to rac The elegance of realization , The first confusing design ）, This subscriber keeps the real subscriber , In the process of subscribing to the signal . For example , That's what you told me subcriber When the signal comes , What are we going to do? .
After creating the signal , Once there are subscribers , That is, the signal is subscribeNext（ For convenience, I will not consider compelete, And error） When ,rac Internally, a subscriber, And this subscriber Saved your executive block.subscriber Actually, it's the same as getting the authorization .
```

QHQSignal *demoSignal = [QHQSignal createSignal:^(id subscriber) {

[subscriber sendNext:@"1"];

}];

[demoSignal subscribeNext:^(id x) {

NSLog(@"%@",x);

}];

```
Simply realized the above code , Is it much simpler . More than one section , It's easy to vomit , And see this .

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